The use of steering systems without a direct mechanical coupling between the steering wheel and the steering gear in motor vehicles is known. Such steering systems are referred to as steer-by-wire steering systems (SbW steering systems). It is necessary in such systems to transmit torques, which correspond to the driving feel of a conventional steering system, to the driver via the steering wheel. Said torques are, for example, torques of inertia and return torques which originate from driving surface influences and steering kinematics. If it is not possible to sense such torques on the steering wheel, safe driving of the motor vehicle by the driver is difficult.
Manual torque adjusters come in various types. It is known in the case of such actuators from U.S. Pat. No. 6,820,713 B2, to create a particularly compact design of the upper steering shaft connected to the steering wheel in an axial direction wherein the required electric motor is arranged axially parallel next to the steering shaft and is coupled to the steering shaft via a belt drive. The electric motor does not extend beyond the length of the steering shaft.
Essential for the acceptance of such steering systems is an extremely precise regulation of the electric motor which generates the manual torque. It is necessary for such regulation to provide the electric motor with a motor position sensor which indicates the current position and, where appropriate, also the angle of rotation speed and direction of the rotor. In known manual torque adjusters, said sensor sits on the free end of the motor shaft which is opposite the output side.
The associated electronics are generally also arranged on the side facing away from the output side of the electric motor. Thus the configuration of the electric motor is extended in an axial direction which is undesirable in particularly compact arrangements. In particular the arrangement of the motor position sensor, also defines the position of the electronic control unit (ECU) of the manual torque adjuster within narrow limits since efforts are made to keep the electric cables between the sensor and the ECU short.
Proceeding from said prior art, the problem to be solved by the present invention is to provide a manual torque adjuster for a SbW steering system which is particularly short in an axial direction.